Hydrindanones angular alkylation

Angular alkylations of lithium enolates of hydrindanones with carbonyl groups in the five- or six-membered rin yield cw-fused products with almost complete stereoselectivity. The lithium enolate of bicyclo [2.2.1]heptan-2-one undergoes exo alkylation with very high stereoselectivity. The presence of a syn methyl group at C-7 reduces the preference for exo alkylation, but it is still preferred over endo alkylation by about 3 1 unless a 5,6-double bond is also present then, endo attack is preferred. The expected steric effects control the stereochemistry of alkylation of other bridged bicyclic systems. - ... 

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